Recording system



April 16, 1940. can KEITH RECORDING SYSTEM Filed Sept. 22, 1938 FIG.

FIG: 3

FIG. 2

FIG. 7

VINVENTOR By C. R. KE /7 H q- -Nqd ATTORNEY Patented Apr. 16, 1940 RECORDING SYSTEM Clyde R. Keith, Maplewood, N. LL, assignor to Electrical Research Products, Inc., New York,

N. Y., a corporation of Delaware Application September 22, 1938, Serial No. 231,159

4 Claims.

This invention relates to apparatus for photographically recording electrical impulses upon a moving light sensitive member, and particularly to apparatus for making a record in the form of a multiple variable area record in which the be as small as possible. I

A feature of the invention is the provision of apparatus for producing a plurality of similar variable area records on a sensitive film so that the effect of inequality of illumination of the reproducing slit will be minimized.

Another feature of the invention is the provision of apparatus for producing two variable area records reversed in phase to permit pushpull reproduction of the records.

A characteristic feature of the invention is a recording light beam masked to form a plurality of right triangles of light, and a shutter formed as a plurality of right triangles arranged to partially obturate the beam.

A further feature of the invention is a mask for the recording light beam sodesigned that the system may readily be changed from the recording of a plurality of similar records to the recording of push-pull records.

In the drawing:

Fig. 1 is a diagrammatic representation of a recorder embodying the invention;

Fig. 2 is a mask for producing multiple records;

Fig. 3 is a mask for producing push-pull records;

Fig. 4 is an enlarged view of a positive print of the record produced by the mask of Fig. 2;

of the record produced by the mask of Fig. 3;

Fig. 6 is a shutter and drive for obturating the recording light; and

Fig. 7 is a mask capable of positional adjustment to produce the records 'of either Fig. 4 or 5. Referring to Fig. 1, light from a suitable source I is directed by the lens 2 upon an opaque mask 3 so as to uniformly illuminate the apertures in the mask 3. The illuminated apertures in the 5 of a recording galvanometer of the usual type. The light beam reflected by the mirror 5 is imaged by the lens 6 upon a narrow slit in the opaque screen i. The light transmitted through the slit in the screen 1 is imaged'by the lens system 8, 9 upon a photographic film l0, moved at constant speed in known manner as by the,

Fig. 5 is an enlargediview of a positive print mask 3 are imaged by the lens 4 upon the mirror area record, the apertures in the mask 3, may have the form of two inverted right triangles as shown in Fig. 2. The optical system is adjusted to bring the vertical sides of the triangular apertures in the direction of motion of the film 5,

and normal to the slitin the screen 1. Before recording, the optical system and the mirror '5 are adjusted to bring the center of the image of the aperture in mask 3 in line with the slit in screen I. 10

For producing a unilateral push-pullvariable area record, the apertures in the. mask 3 'may have the shape illustrated in Fig. -3, .in which only one triangle is inverted. When using the mask shown in Fig. 3, the adjustment of the optical system is substantially the same as for the mask shown in Fig.2.

The masks shown in Figs. 2 and 3 may con-' veniently be combined in one mask as shown in Fig. 7. The mask shown in Fig. '7 will nor- 0 mally be supported in a mounting whichpermits of lateral motion and has some form of stop to limit the lateral motion. When viewed as shown in Fig. 7, by moving the-mask to its extreme right-hand position, the two inverted triangles 25 define the recording beams and a double uni-' lateral record will be produced. By= moving the mask toits extreme left-hand position, the center l and right-hand triangles define the recording Fig. 1, infront of the screen 1. While for convenience of illustration, the shutter I2 is shown some distancein front of the screen i, the shutter 40 I2 would preferably be located very close to the screen 1, ma lens introduced between the shutter l2 and the screen 1.

The noise reduction shutter l2, as shown in Fig. 6, has the'form of two right triangles. The

shutter l2 may be made of any convenient opaque substance, such as sheet metal, and may be mounted on a movable support driven by any convenient means, such as the moving coil mechanism I 3 and field magnet l4. Suitable springs 15 control the movement of the shutter 12.

The vertical edges of the triangles forming the shutter l2, or their images, are aligned with the vertical edges of the images of the apertures in the mask 3 formed at the slit in screen I. The mirror 5 is vibrated by the currents to be recorded and causes the triangular images formed on the slit in the screen 1 to vibrate vertically. The vertical movement of the vertical edges of the images is inefiective to cause any change in the illumination of the slit, but the vertical movement of the sloping edges of the images is effective to illuminate a larger or smaller width of the slit in the screen I and thus to produce an exposure of the film l varying in width or area in accordance with the vibrations of the mirror 5. The coil 13 is actuated by a rectified and filtered component of the currents to be recorded and causes the shutter l2 to move in accordance with the envelope of the amplitude variations of the currents. As indicated in dotted lines in Fig. 2, the shutter 12 obturates more or less of the recording beams, to reduce the exposure of the film In to the smallest amount that will record the movement of the beams.

' Fig. 4 illustrates a positive print of a double unilateral variable area record with noise reduction, which may be produced by the mask in Fig. 2. 'It will be apparent that more than two triangles may be cut in the mask shown in Fig. 2, with 'a corresponding change in the shutter I2,

and thus more than two similar records may be produced.

Fig. 5 illustrates a positive print of a push-pull variable area record, with noise reduction, which may be produced by the mask in Fig. 3, when used in conjunction with the shutter I2, Fig. 6.

What is claimed is:

1. Apparatus for making variable area records on a constantly moving film comprising a source of light, a mirror vibrated by the currents to be recorded to direct light from said source to said film, a screen in the path of the reflected light having a slit extending transversely 'of the direction of movement of the film, a mask in the path of the light impressed on said mirror having a plurality of separate right triangular apertures having no contiguous sides with their vertical sides in the direction of motion of said film and a plurality of separate right triangular shutters having no contiguous sides moved in accordance with the envelope of the currents associated with the light beams transmitted through said apertures, the vertical .edges of said shutters being aligned with the vertical edges of said beams.

2. Apparatus for making variable area records on a constantly moving film comprising a source of light, a mirror vibrated by the currents to be recorded to direct light from said source to said film, a screen in the path of the reflected light having a slit extending transversely of the direction of movement of the film, a mask having a pair of inverted right triangular apertures and an erect right triangular aperture and arranged so that the pair of inverted apertures or one inverted and the erect aperture may at will be inserted in the path of the light impressed on said mirror, and a shutter having a pair of erect right triangles moved in accordance with the envelope of the currents to be recorded to partially inter cept the beams transmitted through said apertures, the vertical edges of said triangles being aligned with the vertical edges of said beams.

3. Apparatus for making multiple unilateral variable area records on a constantly moving film comprising a source of light, a mirror vibrated by the currents to be recorded to direct light from said source to said film, a screen in thepath of the reflected light having a slit extending transversely of the direction of separate movement of the film, a mask having a plurality of inverted right triangular apertures having no contiguous sides in the path of the light impressed on said mirror and a shutter having a separate erect right triangle for each aperture, moved in accordance with. the envelope of the currents to be recorded to partially intercept the beams transmitted through said apertures, the vertical edges of said triangles being aligned with the vertical edges of said beams.

4. Apparatus for making push-pull variable area records on a constantly moving film comprising a source of light, a mirror vibrated by the currents to be recorded to direct light from said source to said film, a screen in the path of the reflected light having a slit extending transversely of the direction of movement of the film, a mask having an inverted and an erect right triangular aperture in the path of the light impressed on the mirror and a shutter having an erect right triangle for each aperture, moved in accordance with the envelope of the currents to be recorded to partially intercept the beams transmitted through said apertures, the vertical edges of said triangles being aligned with the vertical edges of said beams.

CLYDE R. KEITH. 

